Beat egg whites with an electric mixer at high speed until soft peaks form. Add cream of tartar. Add sugar, 1/4 cup at a time, beating after each time, until stiff peaks forms. Add vanilla extract and beat until well blended. Fold in chocolate chips. Drop by heaping teaspoonfuls onto a foiled lined un-greased baking sheet and bake at 250 degrees for 30 minutes. Outside of the cookie will be hard; inside will be slightly soft. Makes 36 cookies.